If the fastening of the cap is weak after the use of the above-described contents, there occurs a problem that the sealed state of the container is not maintained and air or fungi are entered into the container. This causes oxidation of the contents or propagation of mold and accelerates deterioration. In order to solve this, a cap to be mounted on a container mouth section is provided in which an internal pressure is applied to the container by squeezing a body section of the container, and immediately after an appropriate amount of the contents is used, a user seals the container (mouth section of the container) without operating the cap by hand.
For example, Patent Literature 1 discloses a valve device in which a coil spring (generally made of metal) is provided together with a valve body opening or closing a liquid outlet hole in the valve device to be fitted into a container mouth of a container, the container is pressed by squeezing a body section of the container, such that a pressure hole/liquid outlet hole is opened by moving the valve body upward, and after use, the pressure hole/liquid outlet hole is closed by moving the valve body downward by a biasing force of the spring.
Also, Patent Literature 2 discloses that a cap body to be fitted into a container mouth section includes a discharge passage that communicates with the container mouth section, a base section that is fitted into the discharge passage and has a discharge hole, and a check valve that is disposed on the base section and allows only the discharge of the contents from the discharge hole. The check valve includes a cylindrical section fitted into the discharge passage, a plurality of elastic pieces extending radially toward the center such that a gap is formed from an inner wall surface of the cylindrical section, and a valve member integrally connected to a front end of each elastic piece and disposed at a downstream side in a discharging direction of the discharge hole to open or close the discharge hole. When the internal pressure of the container is released, each elastic piece of the check valve is restored. Therefore, the valve member closes the discharge hole and the sealed state of the container is maintained.